1. Field of the Invention
The present invention relates generally to self-propelled exercise devices, and particularly to load wheels that reciprocate along guide tracks of such devices.
2. Related Art
U.S. Published Patent Application No. 2008/0116655 which is incorporated herein by reference in its entirety, as well as U.S. Pat. No. 6,663,127, both disclose a self-propelled exercise device propelled by a drive train in which a user's feet are placed on foot platforms and the user strides forward and rearward to propel the device and thereby derive benefits from exercise. The foot platforms are connected to foot links which are coupled to one or more respective load wheels that reciprocate along guide tracks coupled to the cycle frame. The arrangement is such that the operator's feet travel along closed, reciprocating paths during the pedal stroke. The reciprocating paths may be elliptical or at least partially elliptical in some cases, or may include some circular components.
There are problems in creating a space efficient, low friction, low weight, robust, and inexpensive means for enabling the front end of the foot links of a self-propelled exercise device to reciprocate during the pedal stroke. Alternate approaches are to use a multi-bearing wheel, a bare rotational bearing or various linear bearings.
Using a multi-bearing load wheel would be inferior for numerous reasons. These include making the track system significantly wider, which would increase the weight and cost of the frame and expand the width of the self-propelled exercise device; and increasing the cost and weight of each load wheel because of the additional bearing.
Using a single bare rotational bearing would also be inferior because the load wheel system requires at least one element to provide compliance. Using a bare bearing would require the system to achieve compliance on the track side of the load wheel interface. High-performance self-propelled exercise devices require a track length of at least 14 inches and on some devices the track length can exceed 28 inches. Therefore, covering the track surfaces with a compliant material would require significantly more of the compliant material to be used and would increase the cost and weight of the track system.
A linear bearing, which utilizes recirculating ball bearings, requires a very hard track or rail, which results in a system that is heavier, more expensive and less tolerant to debris and shock loading. A plain polymer linear bearing without rolling elements would be much less efficient than the proposed invention.